CN113614395A - Fluid dynamic pressure bearing device - Google Patents
Fluid dynamic pressure bearing device Download PDFInfo
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- CN113614395A CN113614395A CN202080023337.8A CN202080023337A CN113614395A CN 113614395 A CN113614395 A CN 113614395A CN 202080023337 A CN202080023337 A CN 202080023337A CN 113614395 A CN113614395 A CN 113614395A
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- groove portion
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- bearing
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- IYRDVAUFQZOLSB-UHFFFAOYSA-N copper iron Chemical compound [Fe].[Cu] IYRDVAUFQZOLSB-UHFFFAOYSA-N 0.000 description 1
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Abstract
A fluid dynamic bearing device includes: a shaft member; a bearing sleeve (18) having a shaft member inserted into the inner periphery thereof; and a dynamic pressure groove (26) that supports the shaft member in a non-contact manner so as to be relatively rotatable by means of pressure of an oil film generated in a radial bearing gap between the outer peripheral surface of the shaft member and the inner peripheral surface (24) of the bearing sleeve (18), the dynamic pressure groove (26) comprising: a plurality of polygonal mound portions (27) arranged in a pattern on an inner peripheral surface (24) of the bearing sleeve (18); and a polygonal groove portion (28) formed so as to surround the polygonal mound portion (27).
Description
Technical Field
The present invention relates to a fluid dynamic bearing device.
Background
The fluid dynamic bearing device supports a shaft member in a relatively rotatable manner in a non-contact manner by a pressure generated by a fluid film (for example, an oil film) in a radial bearing gap between an outer peripheral surface of the shaft member and an inner peripheral surface of a bearing sleeve.
Fluid dynamic bearing devices are used by being incorporated into spindle motors of disk drive devices such as HDDs, polygon scanner motors of Laser Beam Printers (LBPs), color wheel motors of projectors, fan motors of electronic devices, and the like, for high rotational accuracy and quietness.
For example, patent document 1 discloses a fluid dynamic bearing device including: a shaft member; a bearing sleeve having a shaft member inserted into an inner periphery thereof; and a radial dynamic pressure generating portion that supports the shaft member so as to be relatively rotatable in a non-contact manner by pressure of an oil film generated in a radial bearing gap between an outer peripheral surface of the shaft member and an inner peripheral surface of the bearing sleeve.
Fig. 16 shows a bearing sleeve 1 constituting the fluid dynamic bearing device of patent document 1. As shown in fig. 16, radial bearing surfaces 3 are formed at two axially separated positions on the inner peripheral surface 2 of the bearing sleeve 1. A radial dynamic pressure generating portion is formed on the radial bearing surface 3. The hollow arrows in the figure show the flow of lubricating oil.
In the bearing sleeve 1 of patent document 1, a herringbone-shaped dynamic pressure generating groove 4 is formed as a radial dynamic pressure generating portion. The dynamic pressure grooves 4 are constituted by mounds 5 (regions shown by scattered dots in the figure) and groove portions 6 located between the mounds 5. In other words, the mound 5 is configured to bulge radially inward from the groove 6.
Documents of the prior art
Patent document
Patent document 1: japanese patent application laid-open publication No. 2011-196544
Disclosure of Invention
Problems to be solved by the invention
However, in the fluid dynamic bearing device described in patent document 1, the rotation direction of the shaft member (see the solid arrow in fig. 16) is limited to one direction. Therefore, when assembling the bearing sleeve 1, the bearing sleeve 1 must be assembled in a direction suitable for the rotation direction of the shaft member, and the assembly work becomes complicated, and the workability is lowered.
Further, since the dynamic pressure generating grooves 4 formed in the inner peripheral surface 2 of the bearing sleeve 1 have a herringbone shape, the bearing area (hill portions 5 of the dynamic pressure generating grooves 4) is reduced. Therefore, the surface pressure applied to the radial bearing surface 3 of the bearing sleeve 1 increases, and the wear resistance decreases.
In addition, in a region where the rotation speed of the shaft member is low, it is difficult to obtain a sufficient dynamic pressure effect, and it is difficult to support the shaft member in a non-contact manner, and the shaft member may contact the radial bearing surface 3 of the bearing sleeve 1.
The present invention has been made in view of the above problems, and an object of the present invention is to provide a fluid dynamic bearing device capable of increasing a bearing area in response to a rotation direction of a shaft member being either a forward or reverse direction, and capable of obtaining a sufficient dynamic pressure effect even in a region where a rotation speed is low.
Means for solving the problems
A fluid dynamic bearing device of the present invention includes: a shaft member; a bearing member having a shaft member inserted into an inner periphery thereof; and a radial dynamic pressure generating portion that supports the shaft member so as to be relatively rotatable in a non-contact manner by a pressure of a fluid film generated in a radial bearing gap between an outer peripheral surface of the shaft member and an inner peripheral surface of the bearing member.
As a technical means for achieving the above object, the present invention is characterized in that a radial dynamic pressure generating portion includes: a plurality of polygonal mound portions arranged in a pattern on either one of an inner peripheral surface of the bearing member and an outer peripheral surface of the shaft member; and a polygonal groove portion formed in a manner of surrounding the polygonal mound portion.
In the present invention, the dynamic pressure generating grooves formed by the polygonal mound portions and the polygonal groove portions are formed as the radial dynamic pressure generating portions, and therefore, the dynamic pressure generating portions can be applied to any of the forward and reverse directions of the rotation direction of the shaft member. In addition, the bearing area of the bearing member (the polygonal mound portion of the dynamic pressure generating groove) can be increased. Further, a sufficient dynamic pressure effect can be obtained even in a region where the rotation speed of the shaft member is low.
In the radial dynamic pressure generating portion according to the present invention, preferably, the polygonal groove portion has a surface aperture ratio larger than a surface aperture ratio of the polygonal mound portion.
With such a configuration, it is effective to supply the lubricating oil to the radial bearing surface of the bearing member efficiently.
Preferably, the radial dynamic pressure generating portion of the present invention has a groove portion for supplying lubricating oil formed in the center of the polygonal mound portion.
With such a configuration, it is effective to supply the lubricating oil to the radial bearing surface of the bearing member satisfactorily, and therefore, the lubrication efficiency is improved.
Preferably, the radial dynamic pressure generating portion of the present invention is formed with a mound portion that prevents the lubricating oil from flowing out of the polygonal groove portion.
With such a configuration, it is effective to prevent the lubricating oil from flowing out of the polygonal groove portion, thereby improving the lubricating efficiency.
Preferably, the radial dynamic pressure generating portion of the present invention has a connecting groove portion connecting adjacent polygonal groove portions, and the cross-sectional area of the connecting groove portion is larger than the cross-sectional area of the polygonal groove portion.
With this configuration, the amount of the lubricating oil flowing through the connecting groove portion is larger than the amount of the lubricating oil flowing through the polygonal groove portion, and the lubricating oil can be continuously supplied to the radial bearing gap.
Preferably, the connecting groove portion of the present invention includes: a first connecting groove portion connecting polygonal groove portions arranged vertically in the axial direction; and a second connection groove portion connected to the polygonal groove portion in the circumferential direction, the first connection groove portion having a larger cross-sectional area than the second connection groove portion.
With such a configuration, even if the center of gravity position of the rotating shaft member is shifted from the design point, the dynamic pressure of the support shaft member can be constant within the range of smoothing, and the structure is robust (robust).
Effects of the invention
According to the present invention, the dynamic pressure generating groove formed of the polygonal mound portion and the polygonal groove portion is formed as the radial dynamic pressure generating portion, so that the dynamic pressure generating groove can cope with even if the rotation direction of the shaft member is any of the forward and reverse directions. Therefore, the assembling work of the bearing member is simplified, and the workability is improved.
In addition, the bearing area of the bearing member (the polygonal mound portion of the dynamic pressure generating groove) can be increased. Therefore, the surface pressure applied to the radial bearing surface of the bearing member is reduced, and the wear resistance is improved.
Further, a sufficient dynamic pressure effect can be obtained even in a region where the rotation speed of the shaft member is low. Therefore, the shaft member can be reliably supported in a non-contact manner, and the shaft member can be suppressed from coming into contact with the radial bearing surface of the bearing member.
Drawings
Fig. 1 is a sectional view showing a schematic structure of a fan motor.
Fig. 2 is a sectional view showing a fluid dynamic bearing device incorporated in a fan motor.
Fig. 3 is a sectional view showing an example of a bearing sleeve of the fluid dynamic bearing device.
Fig. 4A is a cross-sectional view showing the flow of the lubricating oil in the normal rotation of the bearing sleeve of fig. 3.
Fig. 4B is a cross-sectional view showing the flow of the lubricating oil when the bearing sleeve of fig. 3 is reversed.
Fig. 5 is a sectional view showing another example of the bearing sleeve.
Fig. 6 is a sectional view showing another example of the bearing sleeve.
Fig. 7 is a sectional view showing another example of the bearing sleeve.
Fig. 8 is a sectional view showing another example of the bearing sleeve.
Fig. 9 is a table for explaining the cross-sectional area of the connecting groove portion.
Fig. 10 is a table for explaining the surface area of the mound of the dynamic pressure generating groove.
Fig. 11 is a cross-sectional view showing an example of the shaft member.
Fig. 12 is a sectional view showing another example of the shaft member.
Fig. 13 is a sectional view showing another example of the shaft member.
Fig. 14 is a sectional view showing another example of the shaft member.
Fig. 15 is a sectional view showing another example of the shaft member.
Fig. 16 is a sectional view showing a bearing sleeve of a conventional fluid dynamic bearing device.
Detailed Description
Hereinafter, embodiments of the fluid dynamic bearing device according to the present invention will be described in detail with reference to the drawings. Before the fluid dynamic bearing device is described, a fan motor incorporating the fluid dynamic bearing device will be described.
Fig. 1 shows a schematic configuration of a fan motor for cooling which is incorporated in a communication device, for example, a mobile device such as a mobile phone or a tablet terminal.
As shown in fig. 1, the main part of the fan motor includes: the fluid dynamic bearing device 11 of the embodiment; a motor base 13 to which the housing 12 of the fluid dynamic bearing device 11 is fixed; and a rotor 15 to which the shaft member 14 of the fluid dynamic bearing device 11 is fixed.
A stator coil 16 is attached to the motor base 13. Further, a rotor magnet 17 is attached to the rotor 15 so as to face the stator coil 16 with a radial gap therebetween.
When the stator coil 16 is energized, the rotor 15 and the shaft member 14 rotate integrally by an electromagnetic force generated between the stator coil 16 and the rotor magnet 17, and an axial or radial air flow is generated by a blade (not shown) provided in the rotor 15.
Next, the fluid dynamic bearing device 11 assembled to the fan motor, that is, the fluid dynamic bearing device 11 of the embodiment, will be described in detail below.
As shown in fig. 2, the fluid dynamic bearing device 11 of the embodiment includes a shaft member 14, a bearing sleeve 18 as a bearing member, a bottomed cylindrical housing 12, and a seal member 19. The internal space of the housing 12 is filled with a predetermined amount of lubricating oil (not shown).
A rotor 15 (see fig. 1) is attached to the shaft member 14. The shaft member 14 is inserted into the inner periphery of the bearing sleeve 18. The housing 12 has an opening at an axial end and holds a bearing sleeve 18 at an inner periphery. The seal member 19 is attached to an axial end portion of the housing 12 to close an opening portion of the housing 12.
The shaft member 14 is made of metal such as stainless steel, for example, and has a cylindrical shape. The outer diameter of the shaft member 14 is set smaller than the inner diameters of the bearing sleeve 18 and the seal member 19. A projection 20 is provided at the lower end of the shaft member 14. A rotor 15 (see fig. 1) is fixed to an upper end of the shaft member 14.
The housing 12 is a metal or resin member in which a cylindrical side portion 21 and a bottom portion 22 are integrally formed. A receiving member 23 made of resin is disposed on the bottom 22 of the housing 12. The upper surface of the receiving member 23 functions as a thrust bearing surface that contacts the convex portion 20 of the support shaft member 14. The receiving member 23 may be omitted. In this case, the bottom surface of the housing 12 functions as a thrust bearing surface.
The bearing sleeve 18 is cylindrical and fixed to the inner peripheral surface of the side portion 21 of the housing 12 by an appropriate means such as press fitting. The bearing sleeve 18 is a porous body made of, for example, a copper-iron-based sintered metal containing copper and iron as main components. The bearing sleeve 18 is impregnated with a lubricating oil in its inner hollow. The material of the bearing sleeve 18 may be a porous body made of a soft metal such as brass or a resin, in addition to a sintered metal.
A radial dynamic pressure generating portion is formed on an inner circumferential surface 24 of the bearing sleeve 18 as a radial bearing surface. The radial dynamic pressure generating portion supports the shaft member 14 in a relatively rotatable manner in a non-contact manner by a pressure of a fluid film (oil film) generated in a radial bearing gap between an outer peripheral surface 25 of the shaft member 14 and an inner peripheral surface 24 of the bearing sleeve 18.
In this embodiment, as shown in fig. 3, dynamic pressure generating grooves 26 having a polygonal shape, for example, an octagonal shape, are formed as the radial dynamic pressure generating portions. Although the dynamic pressure generating grooves 26 having an octagonal shape are exemplified here, dynamic pressure generating grooves having a polygonal shape other than an octagonal shape may be used.
The dynamic pressure generating groove 26 includes a plurality of octagonal mounds 27 disposed in a pattern on the inner circumferential surface 24 of the bearing sleeve 18, and an octagonal groove portion 28 formed so as to surround the octagonal mounds 27. The octagonal mound 27 has a structure that bulges radially inward from the octagonal groove portion 28 (a region shown by a dotted line in the figure).
The number and size of the octagonal mound 27 and the octagonal groove 28 shown in fig. 3 are only examples, and may be set as appropriate in addition to forming an oil film in the radial bearing gap between the outer circumferential surface 25 of the shaft member 14 and the inner circumferential surface 24 of the bearing sleeve 18.
The dynamic pressure generating grooves 26 are symmetrically shaped with respect to the axial center of the bearing sleeve 18. By arranging the plurality of octagonal mounds 27 and octagonal groove portions 28 in a pattern on the inner circumferential surface 24 of the bearing sleeve 18, a part of the octagonal groove portions 28 is arranged so that the grooves inclined with respect to the rotational direction of the shaft member 14 are bilaterally symmetrical with respect to the shaft center.
The sealing member 19 is an annular member and is made of, for example, a soft metal such as brass, another metal, or a resin. The seal member 19 is fixed to the upper end portion of the housing 12 in a state separated from the upper end surface of the bearing sleeve 18 (see fig. 2).
As shown in fig. 2, the inner peripheral surface 29 of the seal member 19 approaches the outer peripheral surface 25 of the shaft member 14 to constitute a non-contact seal (labyrinth seal). The shape and structure of the sealing member 19 may be other than those shown in fig. 2, and the structure thereof may be arbitrary.
In the fluid dynamic bearing device 11 described above, when the shaft member 14 rotates, a radial bearing gap is formed between the inner circumferential surface 24 of the bearing sleeve 18 and the outer circumferential surface 25 of the shaft member 14. The dynamic pressure grooves 26 of the bearing sleeve 18 generate a dynamic pressure action on the lubricating oil in the radial bearing gap.
When the shaft member 14 rotates at a high speed, an oil film that increases the pressure due to the dynamic pressure action of the dynamic pressure generating grooves 26 is formed in the radial bearing gap between the inner circumferential surface 24 of the bearing sleeve 18 and the outer circumferential surface 25 of the shaft member 14. The oil film forms a radial bearing portion that supports the shaft member 14 in a non-contact manner. The thrust load applied to the shaft member 14 is supported in contact with the upper surface of the receiving member 23 serving as a thrust bearing portion.
In other words, the lubricating oil in the radial bearing gap is collected on the octagonal shoulder 27 side along the octagonal groove portion 28 of the dynamic pressure generating groove 26, and the pressure becomes maximum between the octagonal shoulder 27 and the outer peripheral surface 25 of the shaft member 14. This constitutes a radial bearing portion that supports the shaft member 14 in a non-contact manner. The sliding of the convex portion 20 of the shaft member 14 and the receiving member 23 constitutes a thrust bearing portion that contacts and supports the shaft member 14.
Here, the fluid dynamic bearing device 11 is roughly classified into a dynamic pressure bearing and a perfect circular bearing. The dynamic pressure bearing is a bearing in which dynamic pressure grooves 26 for actively generating dynamic pressure from an oil film in the radial bearing gap are provided in the inner circumferential surface 24 of the bearing sleeve 18. The circular plain bearing is a bearing in which the inner peripheral surface 24 of the bearing sleeve 18 is a cylindrical surface and dynamic pressure is generated by the oscillation of the shaft member 14.
In the fan motor having the fluid dynamic bearing device 11, when used in a normal posture, the shaft member 14, the rotor 15, and the blades rotate with high rotational accuracy due to the pressure-increasing effect by the dynamic pressure grooves 26 as the dynamic pressure bearings, and abnormal noise due to contact between the shaft member 14 and the bearing sleeve 18 is less likely to occur.
Even if the fan motor is used in an abnormal state (for example, in a wobbling state due to the swinging of the shaft member 14), if the shaft member 14 is largely eccentric to the bearing sleeve 18, the ratio of the octagonal hill portion 27 of the dynamic pressure generating groove 26 to the octagonal groove portion 28 is large, and thus a supporting force close to that of a perfect circular bearing can be exerted.
In the fluid dynamic bearing device 11 of the embodiment described above, the dynamic pressure generating grooves 26 formed of the octagonal mound portions 27 and the octagonal groove portions 28 are formed as the radial dynamic pressure generating portions, so that it is possible to cope with both the forward direction and the reverse direction (see the solid-line arrows in the drawings) regardless of the rotational direction of the shaft member 14 as shown in fig. 4A and 4B.
In other words, in the case where the rotation direction of the shaft member 14 is the positive direction, the flow of the lubricating oil is the direction shown by the hollow arrow in fig. 4A. When the rotation direction of the shaft member 14 is reverse, the flow of the lubricating oil is in the direction indicated by the hollow arrow in fig. 4B.
Thus, when the bearing sleeve 18 is assembled, the rotational direction of the shaft member 14 is not limited, and therefore the bearing sleeve 18 can be assembled without being limited in the assembling direction. In addition, the present invention can also be used for applications in which the rotational direction of the shaft member 14 changes. As a result, the assembling work of the bearing sleeve 18 is simplified, and the workability is improved.
In addition, the bearing area of the bearing sleeve 18 (the octagonal mound 27 of the dynamic pressure generating groove 26) can be increased. Therefore, the surface pressure applied to the radial bearing surface of the bearing sleeve 18 is reduced, and the wear resistance can be improved. As a result, the life of the fluid dynamic bearing device 11 can be prolonged.
Further, a sufficient dynamic pressure effect can be obtained even in a region where the rotation speed of the shaft member 14 is low. In particular, the octagonal groove portion 28 functions as an oil reservoir during start-stop and low-speed rotation. This can reliably support the shaft member 14 in a non-contact manner, and thus can suppress contact between the shaft member 14 and the radial bearing surface of the bearing sleeve 18.
The bearing sleeve 18 of this embodiment is a porous body, and the surface aperture ratio in the octagonal mound 27 is 20% or less, preferably 2 to 10%. The surface aperture ratio of the octagonal groove portion 28 is set to be larger than the surface aperture ratio in the octagonal mound portion 27.
With such a configuration, the lubricating oil can be efficiently supplied to the radial bearing surface of the bearing sleeve 18.
As shown in fig. 5, a groove portion 30 (oil groove) for supplying lubricating oil may be formed in the center of the octagonal mound portion 27 on the inner peripheral surface 24 of the bearing sleeve 18. The hollow arrows in fig. 5 show the flow of lubricating oil from the groove portion 30.
By adopting such a configuration, as shown by the hollow arrows in fig. 5, the lubricating oil can be favorably supplied to the radial bearing surface of the bearing sleeve 18, and therefore, the lubricating efficiency can be improved.
As shown in fig. 6, on the inner circumferential surface 24 of the bearing sleeve 18, stepped portions 31 that prevent the lubricating oil from flowing out from the octagonal groove portion 28 may be formed at both axial ends of the inner circumferential surface 24 of the bearing sleeve 18.
With such a configuration, the lubricant can be prevented from flowing out of the bearing sleeve 18 from the octagonal groove portion 28, and thus the lubrication efficiency can be improved.
Coupling groove portions 32 for coupling adjacent octagonal groove portions 28 are formed in the inner peripheral surface 24 of the bearing sleeve 18 of the embodiment shown in fig. 3, 5, and 6. In the dynamic pressure grooves 26, the cross-sectional area of the connecting groove portions 32 is larger than the cross-sectional area of the octagonal groove portions 28. As a precondition, the cross-sectional area of the connecting groove portion 32 is set to be larger than 2 times the cross-sectional area of the octagonal groove portion 28.
For example, the number of grooves in FIG. 9 is 3 and the inner diameter is
In the embodiment of (1), when the depth of the octagonal groove portion 28 is set to 0.003mm and the width W1 is set to 0.1607mm, the cross-sectional area of the octagonal groove portion 28 is 0.0004821mm, i.e., 0.003mm × 0.1607mm2. On the other hand, the depth of the connecting groove portion 32 is set to 0.003mm, the width W2 is set to 0.5315mm, and the cross-sectional area of the connecting groove portion 32 is set to 0.003 mm. times. 0.9517mm, which is 0.0028551mm2。
Here, since the dynamic pressure may be reduced when the cross-sectional area of the connecting groove portion 32 is too large, it is preferable that the cross-sectional area of the connecting groove portion 32 is 0.0028551mm2The following. Therefore, it is preferable to determine the sectional area of the octagonal groove 28 and set the sectional area of the connecting groove 32. Preferably, the depths of the octagonal groove portion 28 and the coupling groove portion 32 are the same as the radial bearing clearance.
As described above, by making the cross-sectional area of the connecting groove portion 32 larger than the cross-sectional area of the octagonal groove portion 28, the amount of lubricating oil flowing through the connecting groove portion 32 is larger than the amount of lubricating oil flowing through the octagonal groove portion 28, and lubricating oil can be continuously supplied to the radial bearing gap. As a result, the lubricating oil in the radial bearing gap can be effectively subjected to a dynamic pressure action in the dynamic pressure generating groove 26.
When the cross-sectional area of the connecting groove portion 32 is smaller than the cross-sectional area of the octagonal groove portion 28, the amount of the lubricating oil flowing through the connecting groove portion 32 is smaller than the amount of the lubricating oil flowing through the octagonal groove portion 28, and a negative pressure is generated in the vicinity of the inlet of the octagonal groove portion 28, so that it is difficult to obtain a sufficient dynamic pressure effect.
As shown in fig. 7, the above-described coupling groove portion 32 (hereinafter, referred to as a first coupling groove portion) couples two adjacent octagonal groove portions 28 arranged vertically in the axial direction of the bearing sleeve 18. Further, coupling groove portions 33 (hereinafter, referred to as second coupling groove portions) are formed to couple the octagonal groove portions 28 arranged vertically in the circumferential direction, respectively.
The first connecting groove portion 32 has an oil reserving function for suppressing shortage of the lubricating oil in the octagonal groove portion 28 and the second connecting groove portion 33. The octagonal groove portions 28 generate a dynamic pressure action, and have a function of suppressing a reverse flow caused by a pressure generated in the second connecting groove portions 33.
The second connecting groove portion 33 has a function of smoothing a pressure peak of dynamic pressure and suppressing eccentricity due to a shift in the center of gravity position of the shaft member 14. In other words, even if the position of the center of gravity of the shaft member 14 is shifted from the design point, the dynamic pressure of the support shaft member 14 can be constant within the range of smoothing, and has robustness (robustness).
Here, it is preferable that the sectional area of the first connecting groove portion 32 is large in order to accumulate the lubricating oil, but when the sectional area of the first connecting groove portion 32 is too large, the flow path length of the octagonal groove portion 28 becomes short, and it is difficult to generate the dynamic pressure to the maximum.
In addition, as a configuration in which the flow path length of the octagonal groove portion 28 is not shortened and the cross-sectional area of the first connecting groove portion 32 is increased, since the axial length of the first connecting groove portion 32 cannot be changed, it is effective to form the recessed portion 34 in which the first connecting groove portion 32 is expanded in the circumferential direction as shown in fig. 8.
On the other hand, although the generation of dynamic pressure can be improved by increasing the flow path length of the octagonal groove portion 28, when the flow path length of the octagonal groove portion 28 is excessively long, the cross-sectional areas of the first connecting groove portion 32 and the second connecting groove portion 33 become small, and the functions of the first connecting groove portion 32 and the second connecting groove portion 33 are reduced.
Further, the second connecting groove portion 33 preferably has a structure with a large cross-sectional area in order to smooth the pressure peak of the dynamic pressure and suppress the eccentricity due to the shift of the center of gravity of the shaft member 14, but when the cross-sectional area of the second connecting groove portion 33 is too large, the flow path length of the octagonal groove portion 28 becomes short as in the first connecting groove portion 32, and it becomes difficult to generate the dynamic pressure to the maximum.
Then, the cross-sectional areas of the first connecting groove portion 32, the octagonal groove portion 28, and the second connecting groove portion 33 are defined as follows. When the cross-sectional area of the first connecting groove portion 32 is A, the cross-sectional area of the octagonal groove portion 28 is B, and the cross-sectional area of the second connecting groove portion 33 is C, A > C.gtoreq.2B is defined (see FIG. 9).
Since the first connecting groove portion 32, the octagonal groove portion 28, and the second connecting groove portion 33 have the same depth, the cross-sectional areas of the first connecting groove portion 32, the octagonal groove portion 28, and the second connecting groove portion 33 are represented by cross-sectional widths in fig. 9. The "number" in the drawings means the number of the two octagonal mounds 27 arranged vertically in the axial direction of the bearing sleeve 18 and arranged along the circumferential direction of the bearing sleeve 18.
As shown in fig. 9, the cross-sectional area ratio a/2B of the first connecting groove portion 32 to the octagonal groove portion 28 is preferably 2.96 or more and 8.26 or less. If the cross-sectional area ratio is less than 2.96, insufficient lubrication oil occurs in the octagonal groove portion 28 and the second connecting groove portion 33, and the dynamic pressure decreases. When the cross-sectional area ratio is larger than 8.26, it is difficult to secure the flow path length of the octagonal groove portion 28, and the dynamic pressure decreases.
Preferably, the cross-sectional area ratio C/2B of the second connecting groove portion 33 to the octagonal groove portion 28 is 2.18 or more and 6.07 or less. When the cross-sectional area ratio is less than 2.18, it is difficult to smooth the maximum peak of the dynamic pressure by the second connecting groove portion 33, and it is difficult to suppress the eccentricity due to the shift of the center of gravity of the shaft member 14. When the cross-sectional area ratio is larger than 6.07, it is difficult to secure the flow path length of the octagonal groove portion 28 and reduce the dynamic pressure, and it is difficult to suppress the backflow of the lubricating oil toward the first connecting groove portion 32 and increase the torque.
In the fluid dynamic pressure bearing device 11, the dynamic pressure generating grooves 26 composed of the octagonal mound portions 27 and the octagonal groove portions 28 are formed as the radial dynamic pressure generating portions, so that the bearing area of the bearing sleeve 18, in other words, the total surface area of the mound portions can be increased, thereby exhibiting a supporting force close to that of a perfect circular bearing. Further, by increasing the surface area of the octagonal mound 27 of the dynamic pressure groove 26, a sufficient dynamic pressure effect can be obtained even in a region where the rotation speed of the shaft member 14 is low, and a supporting force close to that of a perfect circular bearing can be exerted. Further, in the case where the gap between the shaft member 14 and the bearing sleeve 18 is circumferentially offset or inclined with respect to the dynamic pressure effect generated by the octagonal groove portion 28, the dynamic pressure is larger in the direction where the gap between the shaft member 14 and the bearing sleeve 18 is smaller than in the direction where the gap between the shaft member 14 and the bearing sleeve 18 is larger, and thus the eccentricity of the shaft member 14 is suppressed.
As shown in fig. 10, when the total surface area of the inner peripheral surface 24 of the bearing sleeve 18 is D and the sum of the surface areas of the mounds (total surface area of the mounds) in the total surface area D is E, the ratio E/D of the total surface area E of the mounds to the total surface area D is 76 to 78%. Therefore, it is preferable to increase the total hill surface area E of the dynamic pressure groove 26.
The inner peripheral surface 24 of the bearing sleeve 18 varies depending on the number of grooves along the axial direction, but when the surface area of each octagonal bead 27 is represented by F, the surface area ratio F/D between the bearing sleeve 18 and each octagonal bead 27 is 2 to 6%.
When the surface area ratio F/D is less than 2%, the dynamic pressure generating force per octagonal mound 27 decreases, and when the surface area ratio F/D is greater than 6%, the sizes of the first and second coupling groove portions 32 and 33 become smaller, so that the dynamic pressure decreases.
In this embodiment, the angle of the octagonal groove portion 28 with respect to the circumferential direction of the bearing sleeve 18 may be about 15 ° to 45 °. The angle θ of the octagonal groove portion 28 shown in fig. 10 is 40 ° (refer to fig. 7).
As shown in fig. 7, in this embodiment, the axial dimension L1 of the octagonal mound 27 located at the axial center is longer than the axial dimension L2 of the octagonal mound 27 located axially above and below (L1 > L2).
Thus, the center line of the octagonal groove portion 28 through which the lubricating oil flows into the first and second connecting groove portions 32, 33 and the center line of the octagonal groove portion 28 through which the lubricating oil flows out of the first and second connecting groove portions 32, 33 are not aligned linearly, and when the center lines are extended, they come into contact with the octagonal bead portion 27 located at the center in the axial direction, and the center lines do not intersect with each other (see the alternate long and short dash line in fig. 7).
With this configuration, stagnation of the lubricating oil in the first and second connecting groove portions 32 and 33 can be prevented, thereby suppressing loss of dynamic pressure and stabilizing the pressure in the octagonal groove portion 28.
Although the dynamic pressure grooves 26 are provided on the inner circumferential surface 24 of the bearing sleeve 18 in the above embodiment, the inner circumferential surface 24 of the bearing sleeve 18 may be a smooth cylindrical surface and the dynamic pressure grooves 26 may be formed on the outer circumferential surface 25 of the opposing shaft member 14 as shown in fig. 11 to 15.
The embodiment shown in fig. 11 corresponds to the embodiment shown in fig. 3. The embodiment shown in fig. 12 corresponds to the embodiment shown in fig. 5. The embodiment shown in fig. 13 corresponds to the embodiment shown in fig. 6. The embodiment shown in fig. 14 corresponds to the embodiment shown in fig. 7. The embodiment shown in fig. 15 corresponds to the embodiment shown in fig. 8.
Although the receiving member 23 of the thrust bearing portion contacts the convex portion 20 (see fig. 2) of the support shaft member 14 in the above embodiment, the thrust bearing portion may support the shaft member 14 in a non-contact manner by the pressure of an oil film, as in the radial bearing portion of the embodiment.
In the embodiment, the so-called shaft-rotating type fluid dynamic bearing device 11 in which the bearing sleeve 18 is fixed and the shaft member 14 is rotated is exemplified, but the present invention is not limited to this, and a so-called shaft-fixing type fluid dynamic bearing device in which the shaft member 14 is fixed and the bearing sleeve 18 is rotated may be applied.
The present invention is not limited to the above-described embodiments, and various embodiments can be carried out without departing from the scope of the present invention, and the scope of the present invention is defined by the scope of the claims, and includes all modifications within the meaning and scope equivalent to the description of the scope of the claims.
Claims (6)
1. A fluid dynamic bearing device includes:
a shaft member;
a bearing member having the shaft member inserted into an inner periphery thereof; and
a radial dynamic pressure generating portion that supports the shaft member so as to be relatively rotatable in a non-contact manner by a pressure of a fluid film generated in a radial bearing gap between an outer peripheral surface of the shaft member and an inner peripheral surface of the bearing member,
the fluid dynamic pressure bearing device is characterized in that,
the radial dynamic pressure generating portion includes:
a plurality of polygonal mound portions arranged in a pattern on either one of an inner peripheral surface of the bearing member and an outer peripheral surface of the shaft member; and
a polygonal groove portion formed in a manner of surrounding the polygonal mound portion.
2. The fluid dynamic pressure bearing device as claimed in claim 1,
in the radial dynamic pressure generating portion, a surface aperture ratio of the polygonal groove portion is larger than a surface aperture ratio of the polygonal mound portion.
3. The fluid dynamic pressure bearing device as set forth in claim 1 or 2,
the radial dynamic pressure generating portion is formed with a groove portion for supplying lubricating oil at the center of the polygonal mound portion.
4. The fluid dynamic pressure bearing device as set forth in any one of claims 1 to 3,
the radial dynamic pressure generating portion is formed with a mound portion that prevents the lubricating oil from flowing out of the polygonal groove portion.
5. The fluid dynamic pressure bearing device as set forth in any one of claims 1 to 4,
the radial dynamic pressure generating portion has a connecting groove portion connecting adjacent polygonal groove portions, and a sectional area of the connecting groove portion is larger than a sectional area of the polygonal groove portion.
6. The fluid dynamic pressure bearing device as set forth in claim 5,
the coupling groove portion includes:
a first connecting groove portion connecting polygonal groove portions arranged vertically in the axial direction; and
a second connecting groove portion connecting the polygonal groove portions in the circumferential direction,
the cross-sectional area of the first connecting groove portion is larger than the cross-sectional area of the second connecting groove portion.
Applications Claiming Priority (5)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2019059055 | 2019-03-26 | ||
| JP2019-059055 | 2019-03-26 | ||
| JP2020-050522 | 2020-03-23 | ||
| JP2020050522A JP7535865B2 (en) | 2019-03-26 | 2020-03-23 | Fluid dynamic bearing device |
| PCT/JP2020/013255 WO2020196599A1 (en) | 2019-03-26 | 2020-03-25 | Fluid dynamic bearing device |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN113614395A true CN113614395A (en) | 2021-11-05 |
Family
ID=72717402
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202080023337.8A Pending CN113614395A (en) | 2019-03-26 | 2020-03-25 | Fluid dynamic pressure bearing device |
Country Status (2)
| Country | Link |
|---|---|
| JP (1) | JP7535865B2 (en) |
| CN (1) | CN113614395A (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP7213329B1 (en) | 2021-11-29 | 2023-01-26 | シチズンファインデバイス株式会社 | bearing material |
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Also Published As
| Publication number | Publication date |
|---|---|
| JP7535865B2 (en) | 2024-08-19 |
| JP2020165533A (en) | 2020-10-08 |
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